The present invention relates to an improved process for the preparation of 2,2',6,6'-tetratertiary butyl-p,p'-biphenol and p,p'-biphenol by the heterogeneously catalyzed oxidative coupling of phenolic compounds.
Numerous schemes are known in the art to produce self-condensation products by oxidation of phenols. To date, however, a simple process capable of producing 2,2',6,6'-tetratertiarybutyl-p,p'-biphenol and p,p'-biphenol in high yields and selectivities has not been obtained. Generally, prior art processes have been characterized by a low yield of the desired 2,2',6,6'-tetratertiarybutyl-p,p'-biphenol and p,p'-biphenol product, an inability to easily separate the heterogeneous catalyst from the reaction mixture, and poor selectivities toward formation of 2,2',6,6'-tetratertiarybutyl-p,p'-biphenol and p,p'-biphenol reaction product. While heterogeneous catalysts are unexcelled in efficiency in both the oxidative coupling and reduction steps, unless the product can be easily removed for subsequent treatment the greatly increased efficiencies of operation are largely unobtainable to the commercial producer.
We have now found that 2,2',6,6'-tetratertiarybutyl-p,p'-biphenol and p,p'-biphenol may be prepared in high purity and yield and more readily separated and recovered from catalyst and reaction products than heretofore possible.